Miniature shock absorber

Abstract

A miniature shock absorber including an outer tubular housing, an inner tubular housing positioned within the outer tubular housing to define a pressure chamber within the inner housing and an annular accumulator chamber between the housings, a piston mounted for movement in the inner tubular housing, and a piston rod extending out of the front end of the tubular housings for impact by an object to be decelerated. A needle valve is positioned in the rear end of the shock absorber for coaction with an axial passage defined at the rear end of the pressure chamber. The needle valve is threadably received in the rear end wall of the shock absorber and includes an external knob to threadably move the needle valve relative to the axial passage to thereby vary the resistance offered to an impacting object. Return flow of fluid from the accumulator chamber to the pressure chamber occurs through a radial metering port in the inner tubular housing coating with an annular axial passage defined between the piston and a reduced diameter valving portion of the piston rod with the piston shuttling back and forth relative to the piston rod to selectively preclude and allow communication between the pressure chamber and the accumulator chamber. Also disclosed is a stop arrangement, including a stop collar formed as an integral front end portion of the outer tubular housing, to preclude bottoming of the piston against the end wall and to provide precise predetermined end limit positioning for the impacting object.

We claim: 
     
       1. A shock absorber comprising: an outer tubular housing having a front end and a rear end and defining a central axis;   an inner tubular housing having a front end and a rear end, positioned within said outer tubular housing, and defining a pressure chamber within said inner housing and an annular accumulator chamber between said inner and outer housings;   a piston assembly including a piston mounted for reciprocal sliding movement in said inner tubular housing and a piston rod connected to said piston and extending out of said front end of said tubular housings for impact by an object to be decelerated;   port means establishing fluid communication between said pressure chamber and said accumulator chamber proximate the forward end of said pressure chamber;   port means establishing fluid communication between said pressure chamber and said accumulator chamber proximate the forward end of said pressure chamber;   means operative at all times, and irrespective of the fluid pressures in said pressure chamber and in said accumulator chamber, to preclude movement of fluid through said port means from said pressure chamber to said accumulator chamber; and   valving means establishing fluid communication between said pressure chamber and said accumulator chamber proximate the rearward end of said pressure chamber and including means defining an axially extending passage proximate the rearward end of said pressure chamber and a valve member positioned in said passage to define an annular orifice with said passage means, adjustably movable along an axis parallel to said central axis, and operative in response to such movement to vary the size of said orifice and thereby vary the resistance to movement of fluid through said valving means.   
     
     
       2. A shock absorber according to claim 1 wherein said shock absorber further includes: an adjuster member positioned exteriorally of said outer tubular member and operative when moved to adjustably move said valve member and thereby adjust the resistance provided by said valve means.   
     
     
       3. A shock absorber according to claim 2 wherein: said axially extending passage extends rearwardly from the rear end of said pressure chamber coaxial with said axis;   said valve member comprises a needle valve coaxial with said axis and extending forwardly from the rear end of said outer tubular house; and   said adjuster member is connected to the rear end of said needle valve.   
     
     
       4. A shock absorber according to claim 3 wherein: said shock absorber includes a rear end wall rigid with said outer tubular housing; and   said valve member and said adjuster member comprise a single integral member mounted for threaded movement in said rear end wall.   
     
     
       5. A shock absorber according to claim 4 wherein: said adjuster member comprises a knob having an outer diameter approximating the outer diameter of said outer tubular housing.   
     
     
       6. A shock absorber according to claim 2 wherein: said piston rod defines a valving portion proximate its rear end extending between front and rear annular shoulders;   said piston is annular, is positioned on said piston rod valving portion to define an annular axial passageway therebetween, and has an axial length less than the axial length of said valving portion so as to be slidable axially relative to said valving portion;   sliding movement of said piston on said piston rod valving portion between said shoulders is operative to effect selective communication between said annular axial passageway and said port means;   said axially extending passage extends rearwardly from the rear end of said pressure chamber coaxial with said axis;   said valve member comprises a needle valve coaxial with said axis and extending forwardly from the rear end of said outer tubular housing; and   said adjuster member is connected to the rear end of said needle valve.   
     
     
       7. A shock absorber according to claim 6 wherein: said shock absorber includes a rear end wall rigid with said outer tubular housing; and   said valve member and said adjuster member comprise a single integral member mounted for threaded movement in said rear end wall.   
     
     
       8. A shock absorber according to claim 7 wherein: said adjuster member comprises a knob having an outer diameter approximating the outer diameter of said outer tubular housing.   
     
     
       9. A shock absorber according to claim 1 wherein: said piston rod defines a valving portion proximate its rear end extending between front and rear annular shoulders;   said piston is annular, positioned on said piston rod valving portion to define an annular axial passageway therebetween, and has an axial length less than the axial length of said valving portion so as to be slidably axially relative to said valving portion; and   sliding movement of said piston on said piston rod valving portion between said shoulders is operative to effect selective communication between said annular axial passageway and said port means.   
     
     
       10. A shock absorber comprising: an outer tubular housing having a front end and a rear end and defining a central axis;   an inner tubular housing having a front end and a rear end, positioned within said outer tubular housing, and defining a pressure chamber within said tubular housing and an annular accumulator chamber between said inner and outer housing;   a rear end wall rigid with said outer tubular housing;   a piston assembly including a piston mounted for reciprocal sliding movement in said inner tubular housing and a piston rod connected to said piston and extending out of said front end of said tubular housing for impact by an object to be decelerated;   port means establishing fluid communication between said chambers proximate the front end of said pressure chamber;   means operative at all times, and irrespective of the fluid pressures in aid pressure chamber and in said accumulator chamber, to preclude movement of fluid through said port means from said pressure chamber to said accumulator chamber; and   valving means establishing fluid communication between said chambers proximate the rearward end of said pressure chamber and including means defining an axially extending passage extending rearwardly from the rear end of said pressure chamber coaxial with said axis, a needle valve extending through said rear end wall coaxial with said axis to dispose its forward end within said passage to coact with said passage to define a metering orifice, means mounting said needle valve for axial movement relative to said rear end wall so as to vary the size of said metering orifice, and an adjuster knob connected to the rear end of said needle valve and positioned rearwardly of said rear end wall to allow adjusting axial movement of said needle valve.   
     
     
       11. A chock absorber according to claim 10 wherein: said means mounting said needle valve for adjustable movement comprise coacting thread means in said rear end wall and on said needle valve.   
     
     
       12. A shock absorber according to claim 11 wherein: said piston rod defines a valving portion proximate its rear end extending between front and rear annular shoulders;   said piston is annular, is positioned on said piston rod valving portion to define an annular axial passageway therebetween, and has an axial length less than the axial length of said valving portion so as to be slidable axially relative to said valving portion; and   sliding movement of said piston on said piston rod valving portion between said shoulders is operative to effect selective communication between said annular axial passageway and said port means.   
     
     
       13. A shock absorber of the type including an outer tubular housing having front and rear ends and defining a central axis, an inner tubular housing having front and rear ends, positioned within said outer tubular housing, and defining a pressure chamber within said inner housing and an annular accumulator chamber between said housings, port means in said inner tubular housing establishing fluid communication between said pressure chamber and said accumulator chamber, a piston assembly including a piston mounted for reciprocal sliding movement in said inner tubular housing and a piston rod connected to said piston and extending out of the front ends of said housings for impact by an object to be decelerated, and valving means for selectively establishing fluid communication between the pressure chamber and the accumulator chamber, characterized in that the shock absorber includes means operative at all times, and irrespective of the fluid pressures in said pressure chamber and in said accumulator chamber, to preclude movement of fluid through said port means from said pressure chamber to said accumulator chamber and the valving means comprises means defining an axially extending passage extending rearwardly from the rear end of the pressure chamber, a needle valve extending forwardly from the rear end of the shock absorber coaxial with the central axis with its forward end positioned in said passage to define an annular orifice therebetween with the orifice varying in size depending upon the relative axial position of the tip of the needle valve within the passage, and means for selectively moving the needle valve axially to vary the size of the metering orifice and thereby vary the resistance provided by the valving means. 
     
     
       14. A shock absorber according to claim 13 wherein: said means for moving said needle valve axially comprise coacting thread means in the rear end of said shock absorber and on said needle valve and a knob at the rear end of said needle valve to allow rotation of the needle valve to generate threaded movement of the needle valve along said axis.   
     
     
       15. A shock absorber of the type including an outer tubular housing having front and rear ends and defining a central axis, an inner tubular housing having front and rear ends, positioned within said outer tubular housing, and defining a pressure chamber within said inner housing and an annular accumulator chamber between said housings, port means in said inner tubular housing establishing fluid communication between said pressure chamber and said accumulator chamber, a piston assembly including a piston mounted for reciprocal sliding movement in said inner tubular housing and a piston rod connected to said piston and extending out of the front ends of said housings for impact by an object to be decelerated, and valving means for selectively establishing fluid communication between the pressure chamber and the accumulator chamber, characterized in that the shock absorber includes means precluding movement of fluid through said port means from said pressure chamber to said accumulator chamber; the valving means comprises means defining an axially extending passage extending rearwardly from the rear end of the pressure chamber, a needle valve extending forwardly from the rear end of the shock absorber coaxial with the central axis with its forward end positioned in said passage to define an annular orifice therebetween with the orifice varying in size depending upon the relative axial position of the tip of the needle valve within the passage, coacting thread means in the rear end of said shock absorber and on said needle valve, and a knob at the rear end of said needle valve to allow rotation of the needle valve to generate threaded movement of the needle valve along said axis; said piston rod defines a valving portion proximate its rear end extending between front and rear annular shoulders; said piston is annular, is positioned on said piston rod valving portion to define an annular axial passageway therebetween, and has an axial length less than the axial length of said valving portion so as to be slidable axially relative to said valving portion; and sliding movement of said piston on said piston rod valving portion between said shoulders is operative to effect selective communication between said annular axial passageway and said port means. 
     
     
       16. The shock absorber according to claim 15 wherein: said front annular shoulder engages the front annular edge of said piston during decelerating rearward movement of said piston assembly to provide a seal therebetween and preclude communication between said annular axial passageway and said port means and said rear annular shoulder engages the rear annular edge of said piston during extending, forward movement of said piston assembly to allow fluid communication between said port means and said annular axial passageway to thereby allow fluid to flow from said accumulator chamber, through said port means, and through said annular axial passageway to filling the pressure chamber rearwardly of the forwardly moving piston.   
     
     
       17. A shock absorber of the type including an outer tubular housing having front and rear ends and defining a central axis, an inner tubular housing having front and rear ends, positioned within the outer tubular housing, and defining a pressure chamber within the inner housing and an annular accumulator chamber between the housings, a piston assembly including a piston mounted for reciprocal sliding movement in the inner tubular housing and a piston rod connected to the piston and extending out of the front ends of the tubular housings for impact by an object to be decelerated, first valving means establishing fluid communication between the chambers at a relatively forward location, and second valving means establishing fluid communication between the chambers at a relatively rearward location, characterized in that said first valving means is operative at all times, and irrespective of the fluid pressures in said pressure chamber and in said accumulator chamber, to preclude fluid flow from said pressure chamber to said accumulator chamber, and said second valving means includes means defining an axially extending passage proximate the rearward end of the pressure chamber, a valve member positioned in the passage to define a annular orifice with the passage means, adjustably movable along an axis parallel to the central axis, and operative in response to such movement to vary the size of the orifice and thereby vary the resistance to movement of fluid through the second valve means, and an adjuster member positioned exteriorally of the outer tubular housing and operative when moved to adjustably move the valve member and thereby adjust the resistance provided by the second valving means. 
     
     
       18. A shock absorber of the type including an outer tubular housing having front and rear ends, an inner tubular housing having front and rear ends, positioned within said outer tubular housing and defining a pressure chamber within said inner housing and an annular accumulator chamber between said housings, a piston assembly including a piston mounted for reciprocal sliding movement in said inner tubular housing, and a piston rod connected to said piston and extending out of the front end of said housing for impact by an object to be decelerated, characterized in that the piston rod defines a valving portion proximate its rear end extending between front and rear annular shoulders, the piston is annular, is positioned on the piston rod valving portion to define an annular axial passageway therebetween and has an axial length less than the axial length of said valving portion so as to be slidable axially relative to the valving portion, the inner tubular housing includes a port extending radially therethrough, and sliding movement of said piston on said piston rod valving portion between said shoulders is operative to effect selective communication between said annular axial passageway and said port.